Sorry I am jumping in here late and only skimmed the thread. You mentioned you do not have a typical TB, that it is half open at idle. How do you plan to throttle the SC? If you pick a ratio to produce boost at WOT, then that is the permanent drive ratio. Unless you have a way to "choke" the SC, it will try to make boost all the time.

Maybe I missed something and am off-base, maybe this has been sorted already?